1. Field of the Invention
This invention relates to a polyacetal composition which is suitable for molded parts of good wear-resistance that can be used suitably under the condition of repeated friction under high load, regardless of the material of the mating member, and its molded parts.
2. Description of the Related Art
Polyacetal resin has excellent mechanical properties and heat resistance, especially wear-resistance, and it is in wide use as sliding members. However, in case of its use for mechanical parts, such as gears, rollers, bearings, door parts, etc., under the condition of repeated friction under heavy load, improvement of wear-resistance against repeated operations is desired. Also, recently, members with which it comes into contact are becoming diversified, such as plastics, composite plastics or ceramic materials, in addition to conventional metallic materials.
Therefore, conventionally, for the purpose of further improvement of wear-resistance of polyacetal resins, inorganic solid lubricants, such as MoS.sub.2, graphite, etc.; liquid or semi-solid lubricants, such as petroleum, synthetic lubricants, aliphatic alcohols or their esters, etc., or addition of polyolefin fine powder of 500,000 or higher molecular weight are used.
However, wear-resistance of this material varies greatly depending on the material of the mating member and it can be wear-resistant to some mating members, but not wear-resistant to other mating members, therefore a lubricant must be selected depending on the material of the mating member.